SOLVED Duo-Phase distortion

[Jbanks]

Hi folks,

finally got the Duo-Phase up and running. LED’s for the LDR’s power on and I get signal, but it’s just totally distorted and sounds like a synth almost. I tried tweaking the trim pots to no avail to lower the gain.

I’ve included photos of both sides of the board if anyone has any ideas where to start.
I’ll start signal tracing it after I take a break from this pedal. ??

Thanks

 

[zgrav]

Does it distort if you put a really low level signal into the box? Are you getting the same distortion in both channels? Do you hear phasing if you change the amount of light hitting your LDRs? An audio probe may make it easier to isolate your problem(s).

 

[Jbanks]

1) yes it distorts at all volumes. It just gets louder as you turn the feedback pots up
2) yes it’s both channels doing this
3) my Yellow LEDs don’t blink at all. I’ve read that it should be flashing. Does that signal a bad spot somewhere in the LDR’s?
4) no phasing can be heard at all. Either loud distortion or it gets gated and starved off by I believe the transistor.

I’ll start doing a signal trace to see what’s causing the gain.

 

[Robert]

3) my Yellow LEDs don’t blink at all. I’ve read that it should be flashing. Does that signal a bad spot somewhere in the LDR’s?

If your LEDs aren't cycling the LFO isn't running. The LDRs wouldn't cause that.

Can you post a close up pic of the component side of the board with the values visible?

 

[Jbanks]

If your LEDs aren't cycling the LFO isn't running. The LDRs wouldn't cause that.

Can you post a close up pic of the component side of the board with the values visible?

Here’s pics of the left and right sides close up for the component side.

one thing I did do was use a 16 pin socket and an 8 pin socket to cover the 3 TL072 sockets stacked up for IC2, 3, and 4. That shouldn’t affect it because each pin in the socket is independent. So it’s not accidentally pairing 2 TL072’s into each by accident is it???

 

[Robert]

one thing I did do was use a 16 pin socket and an 8 pin socket to cover the 3 TL072 sockets stacked up for IC2, 3, and 4. That shouldn’t affect it because each pin in the socket is independent. So it’s not accidentally pairing 2 TL072’s into each by accident is it???

Nah, that's not a problem.


IC7A and IC7B should be TC1044SCPA charge pumps.

It looks like you have TL072's installed in those spots.

 

[Jbanks]

Thanks so much for spotting that I was wondering why those particular TL072’s were upside down like that. Works great now. I get a pulse from the LEF and sounds great. I think one of my Rate pots isn’t soldered properly as it’s not affecting the sound and chopping it the way the left side does. They should sound identical correct?
But I love the different sounds it can do. From Leslie to crazy vibrato. Lots of options to explore in settings for this. Thanks so much for helping troubleshoot!! ?

 

[Robert]

In normal operation (both toggles down) both sides should behave exactly the same.

Flipping the top toggle switch up syncs Side B to Side A.
Flipping the bottom toggle switch up inverts the sweep on Side B so it sweeps in the opposite direction relative to Side A.


If you set both sides to similar settings are the LEDs pulsing similarly? If not you might need to adjust the trim pots on the side that isn't behaving as expected.

Also, if you hear ticking on the right side (looking at the face of the enclosure) you need to move the wire from the input jack further away from the PCB.

 

[Jbanks]

Ahhh I see what you mean about the switches and which LFO controls what. It does work, I just had to select that switch to control the rate. Now that I’ve seen the LED’s alter I get a sense of what controls what. Thanks for all the help. A great sounding pedal. Super stoked to play around more with it!